Conveyor pulley RPM calculator
Rotational speed of a pulley from belt speed and effective running diameter.
Result
How it works
Pulley speed is needed to check gearbox output speed, size a speed sensor or zero-speed switch setting, and confirm the design belt speed after a pulley or lagging change.
Use the effective running diameter: shell diameter plus lagging on both sides. Lagging wear reduces the diameter and slightly reduces belt speed at the same rpm.
Formula
n = 60,000 × v / (π × D) v in m/s, D in mm, n in rpm
| Symbol | Meaning | Unit |
|---|---|---|
| n | Pulley rotational speed | rpm |
| v | Belt speed | m/s |
| D | Effective running diameter (shell + 2 × lagging) | mm |
Worked example
Inputs: Belt speed v = 1.3 m/s; Effective pulley diameter D = 500 mm.
- n = 60,000 × 1.3 / (π × 500) = 78,000 / 1,570.8
- n ≈ 49.66 rpm
Assumptions and limits
- No slip between belt and pulley.
- Use the effective running diameter, including lagging. For a 500 mm shell with 12 mm lagging, D = 524 mm.
- This result does not establish motor power, gearbox suitability or bearing life.
Screening estimate, not a design approval. Verify measured inputs, current standards, manufacturer limits and site procedures before purchasing, cutting or installation. Isolate and lock out equipment before any hands-on measurement.
Questions
How do I find belt speed from pulley rpm?
Rearrange: v = π × D × n / 60,000. For example 49.66 rpm on a 500 mm pulley gives 1.3 m/s.
Does lagging change the rpm?
For a fixed belt speed, a larger effective diameter gives a lower rpm. For a fixed drive rpm, worn lagging gives a lower belt speed.
Source notes
- Kinematics: belt speed = π × D × n / 60,000 (v in m/s, D in mm, n in rpm).
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